Turbochargers are in wide use today in automobiles and other vehicles to provide increased power and response for the vehicle engines. The turbochargers include a turbine wheel, a compressor wheel and a shaft member connecting together the two wheel members. Exhaust gas from the engine is recirculated into the turbochargers to boost the pressure in the engine and improve performance.
Variable geometry turbine (VGT) turbochargers are designed to allow the effective aspect ratio (A:R) of the turbocharger to be altered as conditions change while the engine is operating. VGTs utilize a ring of rotatable guide vanes to control the flow of exhaust gas into and through the turbine.
VGTs can increase engine power, improve response and have a beneficial effect on emissions. They permit turbine power to be set, providing sufficient energy to drive the compressor at the desired boost level. VGTs are particularly efficient at partial load and minimize or eliminate turbo lag.
The rotatable guide vane members are typically aerodynamically shaped and rotate in unison to vary the gas swirl angle and cross-sectional area. A plurality of spacer members are included adjacent the guide vanes to support the guide ring and mechanical loads. The spacer members, however, often cause disruptions in the gas flow and can reduce efficiency.
It is an object of the present invention to improve the efficiency and performance of VGTs. It is another object to improve the structural integrity of VGTs and reduce the inefficiencies caused by spacer members.